What was found
(CAN) THE AIRCRAFT WAS INVOLVED IN AERIAL LOGGING OPERATIONS, ON A SHORT FINAL APPROACH TO THE LOG LANDING THE AIRCRAFT DEVELOPED A VERY NOTICEABLE HIGH FREQUENCY VIBRATION THAT WAS FELT BY THE FLIGHT CREW THROUGHOUT THE AIRCRAFT INCLUDING THE FLIGHT CONTROLS. THE VIBRATION WAS ALSO ACCOMPANIED BY A VERY LOUD GROWLING NOISE. A SCAN OF THE AIRCRAFT INSTRUMENTS REVEALED NOTHING ABNORMAL. THE PILOT ELECTED TO CONTINUE THE APPROACH TO DROP OFF THE LOAD AT THE LOG LANDING AND THEN MADE A PRECAUTIONARY LANDING AT A NEAR BY LOCATION ON THE BEACH OF THE LAKE. AFTER SHUTDOWN, AN EXTENSIVE INSPECTION OF THE ENTIRE AIRCRAFT CARRIED OUT BY MAINTENANCE PERSONNEL REVEALED A LARGE AMOUNT OF METAL PARTICLES FUSED TO THE INSIDE